This invention relates to a process for the fabrication of a semiconductor die.
Miniaturization and slimming of electrical and electronic equipment has led to a need for both thinner semiconductor devices and thinner semiconductor packaging. One way to accomplish this is to thin down the wafer by removing excess material from the back side of the semiconductor wafer, typically done before the wafer is diced into individual semiconductor dies.
Another solution to produce smaller and more efficient semiconductor packages is to utilize an array of metallic bumps attached to the active face of the wafer. The metallic bumps are disposed to match with bonding pads on a substrate. When the metal is reflowed to a melt, it connects with the bonding pads forming both electrical and mechanical connections. This metallic bump packaging is generally referred to as “flip chip” because the bumped semiconductors are flipped in order to be attached to their substrates.
Due to a thermal mismatch that exists between the semiconductor and the substrate, repeated thermal cycling stresses the metallic interconnections, potentially leading to ultimate device failure. To counteract this, an encapsulating material, commonly called an underfill, is disposed in the gap between the semiconductor and the substrate, surrounding and supporting the metallic bumps.
Current trends in semiconductor packaging fabrication favor completing as many process steps as possible at the wafer level, allowing multiple integrated circuits to be processed at the same time, rather than individually, as occurs after die singulation. However, thinned silicon semiconductor wafers are fragile, so it is a benefit to utilize processes in semiconductor fabrication that do not threaten the integrity of the wafer as it is being diced into individual semiconductor dies and that have as few steps as possible.
One new method for dicing semiconductor wafers into individual dies is called “stealth dicing”. Stealth dicing is a dicing method in which a laser beam is irradiated to the inside of a semiconductor wafer to selected areas, thereby weakening the silicon bonds in those areas, and making it easier to divide the silicon wafer within those areas. Using stealth dicing, very thin semiconductor wafers can be cut without physically stressing the wafer, damage to the wafer is lessened, and die strength of the individual dies is not reduced. It would be an advantage to prepare a wafer for dicing so that the stealth laser dicing can be utilized.